C# softphone with AA, DND, voice call recording - advice

Hi! I needed a .Net sdk for C# softphone development with AA, DND features and some other basic features. I found from many sdks Ozeki Voice over IP sip sdk to be the most flexible, because other softphone feautures e.g., voice call recording (s.p: How to record a voice call?) can easily be added to it and is compatible with many pbxes. Its licenses are costly but the sample programs are available for 20 days.